Mobile communication terminals including portable phones have been downsized and lightened, so that antennas which transmit and receive radio waves are required to be smaller in size and lightened of their weight. A major style of antenna is a built-in antenna, namely, an antenna is always accommodated in a housing of the mobile communication terminal.
FIG. 11 shows a perspective view illustrating a conventional built-in antenna. Antenna element 1 is formed of long and narrow strip of metal plate bent several times over for resonating with radio-wave having a given frequency. The top view of antenna element 1 shows a zigzag line. Base 2 is made of resin and antenna element 1 is fixed thereto. Base 2 shapes like a rectangle which covers the periphery except one end of antenna element 1. Base 2 is generally formed by an insert molding method.
Antenna element 1 has coupling terminal 3 at its one end, and terminal 3 protrudes from a lateral face of base 2 to the outside, so that conventional antenna 5 has a mono-pole structure. Such conventional antenna 5 is coupled to a circuit pattern of a circuit board (not shown) disposed in a housing (not shown) of the device at its coupling terminal 3 by soldering. Antenna 5 is thus always accommodated in the housing of the device and coupled mechanically as well as electrically to the circuit of the device via coupling terminal 3. A given operation to the device by its user allows the device to receive or transmit radio wave via antenna 5, so that the user can start communication. Meanwhile, Japanese Patent Application Non-examined Publication No. 2003-32022 is prior art of the present invention.
Since mobile communication devices including portable phones have been rapidly downsized and lightened recently, a place for accommodating the built-in antenna has been gradually reduced in the device, and yet, the rectangular volumetric-shape is not always kept but an irregular shape is often prepared for the antenna.
When an external appearance of an antenna is designed to be an irregular shape, conventional antenna 5 needs to adjust each one of bent points of the zigzag of antenna element 1 to fit the external appearance of the antenna. If the insert molding method is used for burying antenna element 1 in base 2, an insert metal-mold having complicated press-pin positions is required. As a result, antenna 5 becomes expensive.